Power distribution

Abstract

Several aspects of power distribution systems are described. One aspect relates to apparatus for providing a direct current to a load comprising one or more light emitting diodes. The apparatus comprises: a rectifier operatively connectable to a secondary winding of a transformer whose primary winding is for carrying a high-frequency alternating current; a first capacitor operatively connectable to the secondary winding; and a second capacitor operatively connectable, at least partly via the rectifier, to the secondary winding. The first and second capacitors together provide a reactance referred to the primary winding which substantially compensates for the reactance of the primary winding.

The invention claimed is: 
     
       1. Apparatus for providing a direct current to a load comprising one or more light emitting diodes, the apparatus comprising: a rectifier operatively connectable to a secondary winding of a transformer whose primary winding is for carrying a high-frequency alternating current; and a switch configured to periodically interrupt a current originating from the rectifier, thereby reducing an average level of the direct current provided to the load, wherein:
 the apparatus comprises a first inductor configured to smooth the current originating from the rectifier, thereby providing a first current; 
 the switch is configured to periodically interrupt the first current, thereby providing a second current; and 
 the apparatus further comprises a second inductor configured to smooth the second current. 
 
     
     
       2. Apparatus according to  claim 1 , wherein the alternating current has a frequency of at least 10 kilohertz. 
     
     
       3. Apparatus according to  claim 1 , wherein the switch is not comprised in the rectifier and wherein the switch is configured to periodically interrupt the current originating from the rectifier by completing a path therefor between first and second outputs of the rectifier. 
     
     
       4. Apparatus according to  claim 1 , wherein the switch is configured to interrupt the current originating from the rectifier with a frequency which is equal to a frequency of the current originating from the rectifier, a multiple thereof of the said frequency or a factor thereof of the said frequency. 
     
     
       5. Apparatus according to  claim 1 , wherein the switch is configured to interrupt the current originating from the rectifier for a pre-set and/or controllable fraction of the time. 
     
     
       6. Apparatus according to  claim 1 , comprising: a first capacitor operatively connectable to the secondary winding; and a second capacitor operatively connectable, at least partly via the synchronous rectifier, to the secondary winding, wherein the first and second capacitors together provide a reactance referred to the primary winding which substantially compensates for the reactance of the primary winding.